P21: Reduction of Cardiac Pre-Load Has Antithetical Effects on Blood Pressure and Arterial Stiffness: is Blood Pressure The Main Determinant of Within-Subject Variation in Pulse Wave Velocity?

Abstract

Objective

Blood pressure (BP) is considered the most important determinant of within-subject variation in pulse wave velocity (PWV) and the possibility of altering arterial stiffness independently of BP is still a matter of debate. When investigating acute effects of a reduction in cardiac preload, we hypothesised that this would decrease BP and PWV.

Design and methods

Hypertensive patients (mean ± SD age 44 ± 14 years, n = 45) had brachial BP measurements (OMRON), central BP recorded by radial pulse wave analysis (SphygmoCor) and estimation of aortic PWV (aoPWV) by trans-thoracic echocardiography. Carotid-femoral PWV (cfPWV) was also evaluated by SphygmoCor in n = 17. Measurements were performed before and after (>5 minutes) supra-diastolic, sub-systolic pressure inflation of thigh cuffs in order to decrease venous return from the lower limbs. Evaluation of inferior vena cava (IVC) diameter was used to assess pre-load.

Results

Leg cuff-inflation was effective in reducing cardiac pre-load (change in IVC diameter (mean ± SE) from 1.6 ± 0.4cm to 1.3 ± 0.4cm, p < 0.01) and decreased both brachial and central SBP (−3 ± 0.9mmHg and −3.6 ± 1.2mmHg respectively, both p < 0.05) while change in DBP (0.8 ± 0.9mmHg) and heart rate (−0.1 ± 0.6 bpm) were not significant. By contrast, aoPWV increased by 0.8 ± 0.35m/s (p<0.01) and cfPWV by 1.05 ± 0.33 m/s (p = 0.014).

Conclusions

Contrary to our hypothesis, acute reduction of cardiac preload significantly decreased BP but had an opposite effect on PWV. This could be mediated by an increase in sympathetic tone triggered by reduction in circulating blood volume; sympathetic tone might affect PWV independently of BP.